2018 Elements, Atoms and Bonding Rho Pre-mid Term Quiz

A scientific theory is a well-tested idea that explains and connects a wide range of observations. It goes beyond just describing nature's behavior and provides an explanation for how things work in nature. This explanation is based on evidence and has been tested through experiments and observations. A scientific theory is not just a method of inquiry, but rather a comprehensive explanation that helps us understand the natural world.

Rutherford's Gold Foil Experiment involved firing alpha particles at a thin sheet of gold foil. The majority of the alpha particles passed straight through the foil, but a small fraction were deflected or bounced back. This led Rutherford to conclude that atoms have a small, dense, positively charged nucleus at their center, around which the negatively charged electrons orbit. This explanation is supported by the observation that most of the alpha particles passed through the gold foil, indicating that atoms are mostly empty space.

The correct answer is that all matter is composed of one element or a combination of two or more elements. This is because elements are the fundamental substances that cannot be broken down into simpler substances by chemical means. Matter, on the other hand, refers to anything that has mass and occupies space. Therefore, matter is made up of elements, either as pure substances or as combinations of different elements.

Oxygen is not a mixture because it is an element. A mixture is a combination of two or more substances that are physically combined and can be separated by physical means. Oxygen, on the other hand, is a pure substance that cannot be broken down into simpler substances by physical or chemical means. Therefore, it is not considered a mixture.

Democritus proposed the idea that matter is made up of very small pieces that cannot be divided further and still retain their properties. These small, indivisible particles are called atoms. It took 2000 years for Democritus' idea to be accepted, but eventually, the concept of atoms became a fundamental principle in chemistry and physics. Atoms are the building blocks of matter and combine to form molecules, ions, and elements.

A compound is different from an element because it is made of two or more elements chemically combined. Unlike elements, which are made up of only one type of atom, compounds consist of different types of atoms bonded together in specific ratios. This chemical combination results in new properties and characteristics that are distinct from the individual elements. Therefore, a compound is a unique substance formed by the chemical union of multiple elements.

John Dalton's atomic model is still accepted today because it proposed that atoms are indivisible and cannot be broken down into smaller pieces, similar to a smooth and solid lacrosse ball. This model laid the foundation for understanding the structure of matter and the concept of atoms as the building blocks of all substances. Despite advancements in atomic theory, Dalton's idea of atoms being fundamental particles has stood the test of time.

Chadwick is the correct answer because he is the scientist who discovered the neutron, which is a particle in the nucleus of an atom. The neutron is hard to detect because it has no electrical charge, but it has nearly the same mass as a proton. Chadwick's discovery of the neutron completed the modern atomic model.

All the atoms of a single element have the same number of protons. This is because the number of protons in an atom determines its atomic number and defines the element. Different elements have different numbers of protons, which is why they have different atomic numbers and are classified as separate elements. Neutrons and electrons, on the other hand, can vary in number within atoms of the same element, leading to different isotopes and ionization states. The nucleus is the central part of an atom that contains protons and neutrons, but it is not directly related to the statement that all atoms of a single element have the same number of protons.

John Dalton's atomic theory states that all atoms of the same element are exactly alike and have the same mass, atoms of different elements are different and have different masses, an atom of one element cannot be changed into an atom of a different element, atoms cannot be created or destroyed in any chemical change, only rearranged, every compound is composed of atoms of different elements combined in a specific ratio, and all elements are composed of atoms that cannot be divided. However, it does not mention anything about atoms having no overall electrical charge because each atom has the same number of electrons as protons.